The BBN Butterfly Parallel Processor can support a user model of computation that is based on either shared memory or message-passing. A description is given of the results of experiments with the message-passing model. The goal was to analyze the tradeoffs between the shared memory model, as exemplified by the BBN Uniform System package, and a simple message-passing model. The two models are compared with respect to performance, scalability, and ease of programming. It is concluded that the particular model of computation used is less important than how well it is matched to the application.